The invention provides a method for measuring the maturity of the parent oyster gonad, and further provides specific application of the method for measuring the maturity of the parent oyster gonad. The method comprises the steps that firstly, parent oysters are selected according to the reproductive biological characteristics of different oysters; then heating is carried out for mature promoting culture; the parent oysters in mature promoting culture are randomly selected every other 7-10 days, complete soft parts are taken out through dissection, the cross sections of the centers of the soft parts are obtained, the minimum diameter A of the whole cross sections and the minimum diameter B of the digestive diverticulum of the same cross sections are measured, then the gonad index of the parent oysters is calculated through (A-B)/A*100%, an average value is taken, and the gonad index in a corresponding measuring time period is obtained. According to the method, the gonad index of the oysters is accurately measured, and the problem that the gonad index of the oysters is hard to accurately measure is solved. Egg laying time can be accurately grasped for indoor heating young oyster culture, and a guarantee is provided for accurate young oyster collecting in the sea area.